Specific diagnoses of minimal brain dysfunction have not been made for children in the longitudinal Collaborative Perinatal Project, but there is information available related to the most frequently cited symptoms (e.g., hyperactivity, learning difficulties, and equivocal neurological signs). This study will attempt to develop MBD criteria from the available CPP data, characterize MBD children in terms of demographic, psychological, and physical variables, and relate MBD or its components or individual symptoms to socio-economic, maternal, neonatal, perinatal, and other antecedent variables. Antecedent variables to be investigated will be selected from among family characteristics, maternal characteristics, the prenatal period, labor and delivery variables, the neonatal period, infancy and childhood characteristics, and intercurrent events. It is expected that a minimum of 300 antecedent variables will be examined. The selection and definition of many of these variables will be in collaboration with investigators in other primary areas. Based on test data already received, the following preliminary observations are possible: (1) The risk of problems in one area is increased between 40% and 100% if a child has problems in one of the other four areas. That is, there is a significant association among the symptoms in the four areas. (2) Most children, however, who have problems in one area (e.g., physical) do not have problems in the other areas (e.g., behavioral or academic). In other words, the association among symptoms is not a strong one. (3) Correlations and factor analyses of the individual symptoms have identified four major factors that will be studied in detail. These include academic problems, minor neurological problems, hyperactivity-impulsivity, and "socio-emotional immaturity."